[1] Goethe Univ Frankfurt, Inst Organ Chem & Chem Biol, Ctr Biomol Magnet Resonance BMRZ, Max von Laue Str 7, D-60438 Frankfurt, Germany
[2] Univ Iceland, Inst Sci, Dept Chem, Dunhaga 3, IS-107 Reykjavik, Iceland
[3] Goethe Univ Frankfurt, Inst Phys & Theoret Chem, Ctr Biomol Magnet Resonance BMRZ, Max von Laue Str 7, D-60438 Frankfurt, Germany